The Possibilities of Potions
by Hour of Twilight
Summary: When Twilight invites Rainbow Dash over to help her out in her quest to catalog a selection of borrowed potions, she figures she's in for a few boring hours of sorting through bottles and writing down numbers. After a few samples, however, the two ponies stumble upon a bottle that transforms Rainbow into a stallion. Unsure at first, Twilight and Rainbow become determined to documen
1. Chapter 1

Rainbow Dash touched down lightly on the grass. Ahead of her, the branches of the giant tree swayed gently in the summer breeze. Twilight Sparkle's home, formerly a symbol of boredom and eggheadedness, had become a welcome sight since Rainbow had discovered the adventures of Daring Do three weeks ago. Still, as fun as reading her adventure stories could be, Rainbow had other things she wanted to be doing. Her wing was finally back in top shape, and she was dying to keep practicing her latest aerial maneuver, the Dashing Dazzler.

But a friend was a friend. Rainbow sighed, and held up the note again.

Dear Rainbow Dash,

I'm extremely sorry to bother you, and I know you must be busy, but I really need your help. If you have a few hours, could you meet me at the library around noon tomorrow?

Sincerely, Twilight Sparkle.

Rainbow sighed again. Knowing Twilight, she was shelving books or something, and needed an extra set of hooves. She'd help, but she didn't think she'd enjoy it.

The door was shut tight when she arrived. Rainbow gave it a firm knock, waited for a moment, and then yelled, "Hey, Twilight! You in there?"

The top half of the door swung open. Twilight beamed at her through the opening. "You're here! Excellent, we can get started right away." She opened the bottom of the door and let Rainbow inside.

"So what did you need help with?" asked Rainbow, trying to hide her impatience.

"Sorry, Rainbow Dash." Twilight looked sheepish. "Normally, I'd ask Spike or Pinkie to be my guinea pig, but Spike's visiting Canterlot on business for the Princess, and Pinkie's out of town—she mentioned something about a balloon tying competition." Twilight shrugged. "Anyway, I need an assistant to help me catalog these items for study."

Rainbow suppressed a groan. Cataloguing items? Great. This is going to be more boring than watching Tank try to play catch without his magicopter. She forced a smile. "What items?"

Twilight gestured behind her. The center of the library was occupied by a table covered with several boxes. Rainbow could see the tops of bottles poking out of them. She raised an eyebrow. "You're not going to blow anything up this time, are you?"

"Hopefully not." Twilight's horn glowed, and one of the bottles rose from the box. It was filled with a clear, blue-tinted liquid. "These are potions that Zecora brewed for me. I asked her to give me a decent sampling of everything she knew how to make."

"Er..." Rainbow leaned back. "You're not sick or anything, are you?"

"No, no, they're not all cures like her poison joke recipe." Twilight set the potion down on the table, and scanned a sheet of paper lying beside the boxes. "Zebra magic is completely different from unicorn magic. We channel spells through our horns, but they use herbs and potions, among other things. What's really interesting is that their alchemy can produce unique reactions and effects unseen in-"

Rainbow held up a hoof. "Whoa, Twilight, you're losing me."

Twilight rolled her eyes. "Zebras can do things unicorns can't. I want to figure out how."

"And you're going to do that by cataloguing all these potions?"

"That's just the first step. The second—and more important—step is where I need your help." Twilight smiled. "We're going to test them out! And monitor the effects, of course."

"Wait, you're going to have me drink a bunch of random magic potions?"

"Not random!" Twilight pointed back at the boxes. "I've labeled each set. These are the health brews, those are stimulants—I'm certain they're why Zecora's coffee is so strong—and this box has the most interesting bottles of them all." She lifted the box labeled Alteration Potions off of the table, and set it down on the floor.

"Alteration?" Rainbow swallowed. "What's going to happen? Will they turn me into a giant bug or something?"

"Nothing that drastic." Twilight held up another bottle and shook it, eyeing the mixture. "But zebras can do some incredible things. Like age magic. It takes an extremely powerful unicorn to perform an age spell, but I've read about zebra potions transforming ponies into fillies and grandparents in an instant. I'm determined to figure out just what it is about these mixtures that produces such powerful effects."

"I don't know about this..." Rainbow eyed the box warily. "Are you sure it's safe?"

"I wouldn't ask you if I wasn't." Twilight smiled reassuringly. "But we'll only do this if you're okay with it."

Come on, Rainbow, she's counting on you. With her jaw set, Rainbow nodded. "All right, Twilight."

"Great! I've got everything ready, we just need to start going through the potions one by one and record the effects. I'll scan you for any magical auras and then administer the reversal agent." Twilight's horn glowed again, and one of the bottles rose from the box to float over to hover in the air, level with Rainbow's head.

She took a deep breath, and grabbed the bottle in her teeth. Tipping her head back, she drank. The liquid burned mildly in her mouth as it went down, and she grimaced. "Tastes like mouthwash."

"Hmm... it doesn't have any alcohol content. I wonder what's causing that sensation..." Twilight scratched some notes on her paper with a quill.

Rainbow bounced nervously on her hooves. "Am I turning into a giant bug?"

Twilight's eyes widened slightly. "See for yourself."

Looking down at her hooves, Rainbow found to her surprise that they were rapidly turning gray. The color seemed to be leaking out of her skin and evaporating into thin air. "Is this... is this supposed to happen?"

"Well, number forty-seven was labeled 'Desaturation Draught.' Oh, my! Your mane's going too!" Twilight blinked.

Rainbow felt a flash of panic. She pulled her mane over in front of her face and squeaked. All the colors in her vibrant hair had been washed out. She looked like somepony from a moving picture on the weather patrol's ancient projector. "Fix it!"

"Just a moment," said Twilight, closing her eyes. Her horn glowed, and Rainbow felt a tingle as Twilight examined the pegasus for magical effects. "How interesting," she murmured.

"Great, great, interesting, can we please get my color back?"

Twilight's eyes snapped open. "Sorry, sorry! Let me get the antagonist." She dug into the box, rifling through several bottles before pulling out a red one. "Here we go, 'Creme de Color.' Just a mouthful, you don't want to be walking around in neon." Twilight handed her the potion, and she poured it down her throat.

Slowly, Rainbow felt a warm, pleasant sensation bubbling up through her. She watched her mane intently, and was relieved to see it blossom into color like a blooming flower. "None of these are going to be permanent, are they?"

"They shouldn't be." Twilight sorted through the box, looking for the next bottle to try out. "Zecora told me she'd intentionally made light doses. They should wear off in a few hours if we don't reverse them earlier than that."

The next potion tasted sweet, like honey. Rainbow licked her lips. "I like this one."

Twilight waited for a few moments, and then frowned. "It doesn't look like anything's happening."

"I don't feel any different." Rainbow blinked. "Hang on, I'm seeing—you look weird."

"Huh?"

"It's like you're glowing, or something, and the candles are, too." Rainbow made a little ooh sound.

"Really! It sounds like you're seeing in the infrared spectrum, Rainbow Dash." Twilight's quill scratched furiously. "I'm saving that one to use with my telescope." She set the bottle aside.

They continued testing potions. Rainbow found herself beginning to enjoy the experiments. Some of the potions did strange things to her, like the one that made her tail and mane start growing uncontrollably, but others were undeniably cool, like the one that turned her waterproof. They tested that one out by dumping a bucket of water over her. All the water just splashed to the floor, leaving Rainbow totally dry. Twilight got rid of the mess with a handy liquid-removing spell she'd learned a few months ago.

"Let's do this one next," said Twilight, holding up a bottle of black liquid.

Rainbow chugged the bottle, setting it down and wiping her lips. "Well?"

Twilight's eyebrows shot up. "Rainbow!"

"Hmm?" Rainbow looked over her back to see if she'd turned purple again, and froze in shock. Her feathers were falling out.

"Ahhh!" she yelled, flapping her wings frantically. More feathers drifted slowly to the ground. "Fixitfixitfixit!"

Twilight rummaged through the box. "Hang on, hang on... no, no, not that one, no, no, no... Where'd number sixty-two go?"

Rainbow shoved her aside and scanned the bottles with the sharpest eyes in Ponyville. She spotted sixty-two, and reached down to snag it. Quickly pulling out the stopper, she drank the potion in a swift gulp.

The seconds passed, but her wings continued to molt. She blinked at Twilight. "You said sixty-two, right?"

"Yes! 'Feather Fizz' should've fixed this, I don't—" Twilight paused.

"What?" Rainbow tilted her head.

"I don't think you drank the right potion..."

Suddenly, Rainbow felt a bizarre stretching sensation. Her muzzle felt like it was expanding, jutting out and becoming blockier. Her legs bent suddenly as they, too, began stretching. They thickened, the curves of her legs straightening.

Her face contorted with discomfort, and she groaned, "Quick, give me the right one!" Twilight pulled up a bottle, checked the number, nodded to herself, and then stuck it in Rainbow's mouth. She chugged it, and suddenly her wings felt like pincushions. A thousand tiny needles poked her wings, as new feathers burst forth to replace the ones now lying on the ground.

"Thank Celestia." Rainbow's voice sounded strange to her ears, slightly deeper than normal. Another bout of stretching pain came over her, and she twisted. "Ow! What—what did I drink?"

The next change made it suddenly clear. Rainbow felt a new, unfamiliar something brush against her stomach. Even more strange, the brushing sensation wasn't coming from her belly itself. The obvious answer was too ludicrous for her to consider right away.

"Well," said Twilight, her voice slightly higher-pitched than usual, "I think we found the stallion transformation potion."

"St-stallion transformation?" Rainbow's voice was definitely lower than normal. She blinked, staring down at her too-large hooves. "I didn't think you could—"

"Unicorns can't," said Twilight, still looking a little alarmed. "Like I said, zebra magic can do some weird things."

"Uh." Rainbow blinked. She—he?—no, Rainbow decided, still she; whatever her physical body, inside she was still the same old Rainbow Dash.

But what the hay was going on with her body?

"Fascinating," said Twilight, walking around her with her notebook. "The transformation seems pretty thorough. Your anatomy is totally different."

Anatomy? Rainbow swallowed. "Er..."

"Your bones are much blockier, and your legs are thicker. Hmm..." Twilight jotted down more notes. "I wonder how deep the transformation goes. You think your chromosomes have changed?"

"My kroma-whats?" Rainbow felt a drop of sweat drip down her forehead. "Er, do you think we could change me back now?" She felt very strange. Her body was too heavy, weighted down by all the extra bone and muscle mass.

"Wait a minute or two, I'd like to get some data on this. It's one of the first uniquely zebra magical effects we've come across today." Twilight poked Rainbow's flank, making her jump.

"Hey!"

"Sorry. Subject reacts to stimuli... nerves appear fully functional." Twilight paused as her quill ran dry, and moved back to re-ink it.

Rainbow took the opportunity to examine her new—and, she trusted, temporary—body. Her mane felt coarser, and her mouth was bigger. She felt taller, too. Though she was definitely not built as big as, say, Applejack's brother, she could look over Twilight's head without stretching her neck, now.

And then there was the other thing. The thing that had appeared between her legs, in the most unexpected attack of stretching. She looked up at Twilight. Seeing the unicorn still absorbed in her notes, Rainbow turned her back, and sat down to examine her new body part.

It was half-extended from its sheath, a marbled blue-and-black shaft with a flattened head. Rainbow blinked, still not quite believing it. A dick. I have a dick.

A tiny voice in her head piped up, I wonder how it feels?

She quashed it instantly, blushing. Hopefully, Twilight would finish her notes and give Rainbow the antidote soon. Then she'd be back in her old body, and wouldn't have to deal with all these new sensations.

Seems like a shame to lose it without even trying it out, though.

Did stallions always think like this? Granted, Rainbow had met a few with one-track minds, but she had hoped it wasn't universal. Despite her efforts to turn her mind to other things, she couldn't help but stare at her slowly hardening member.

"All right, Rainbow Dash, I'd like to get a sample of your tissue."

Rainbow heard Twilight's hooves thud on the floor and jerked upright. "Wait, what?" She twisted her head to see Twilight approaching with a syringe held by her magic. "Whoa, you're not planning to stab me with that, are you?"

Twilight held up a calming hoof. "Relax, Rainbow, it won't hurt very much. I just need a blood sam—sample, to—uh..." Her eyes widened.

Rainbow realized that when she'd turned, she'd revealed her half-stiff cock to her friend. Her face went beet-red. "Um."

"A... very thorough transformation." She bit her lip, and whispered under her breath, "I wonder if that's why they made the recipe..."

Rainbow pretended not to hear. "Look, can I please take the anti-whatever now?"

"I still need a tissue sample." Twilight half-opened her mouth, then bit her lip. "If you don't want to use the needle, there's another way."

"Okay, fine, whatever gets me back to being me." Rainbow wiped her forehead.

"It might be for the best, anyway. I'm curious if... well, if that is functional."

Rainbow gave her a scandalized look. "You want me to pee?"

"Well, no." Twilight looked sheepish. Her cheeks tinged pink. "There's no DNA in urine."

"You mean—" Rainbow choked. "Uh, Twilight, you're saying you want me to, like... get off?"

"For posterity," said Twilight, a little too quickly. "Besides, aren't you curious?"

Extremely. "Not really..." Rainbow sat back on her haunches, staring down at the lengthening shaft of her stallionhood. "But I guess... I mean, if it's this or getting stabbed, I guess I'll take this." She swallowed. "So. Uh."

Twilight was looking quite flustered by now. "I suppose you ought to, um, stimulate yourself."

Rainbow lifted a hoof and looked at it uncertainly. She slowly brought it down to rest on her hardening dick. It felt hard and soft at the same time, like velvet over iron. Slowly, she ran her hoof down the length of her shaft, inhaling at the touch.

She moved her hoof back up to the top and rested it there, watching as a tiny white bead emerged from the tip. Well, there's Twilight's sample, she thought dryly, but she continued moving her hoof across her head. It smeared the tiny drop of liquid across the flared tip of her cock, and she felt it twitch. She spared a glance up at Twilight, who was watching intently.

Rainbow began moving her hoof up and down, feeling it slide along her sensitive skin. She breathed deeply, matching her slow strokes. Her cock was beginning to ache with need. She gritted her teeth and continued to rub it softly.

Motion drew her attention. Twilight looked extremely uncomfortable, standing stiffly with her lips pressed together. Why is she looking nervous? I'm the one playing with myself in front of her. Rainbow closed her eyes and breathed out. She had to admit, this felt good.

She brought her other foreleg over and began rubbing both of her hooves along the sides of her stallionhood. Every time they passed over the little ring in the middle of her length, she felt a tiny tingle of pleasure.

Twilight cleared her throat. "So, Rainbow, ah... how's it feel?"

"Really... mmm, really good." Rainbow began stroking faster, tugging on herself with every upward stroke. She folded her right wing around her shoulder, and bit down on her tip feathers like she always did when she played with herself. Granted, usually she didn't need both hooves...

Her head was getting cloudy with heat and anticipation. Increasing the pace of her strokes, she gave another murmur of excitement. The throbbing feeling in her cock was only getting stronger, but it was a good kind of pain. She licked her lips.

Sparing another look up at Twilight, Rainbow found her friend staring wide-eyed and sweating. She grinned, as her inner performer took over. Whether it was aerial maneuvers of daring skill, or slippery, hot self-pleasure, Rainbow Dash was comfortable in front of crowds. She tilted her head back. "Enjoying the show?" she asked, joking.

To her surprise, Twilight blushed redder, and squeezed her back legs together. "Very... educational."

Rainbow raised an eyebrow. "Educational, huh?" She took her hooves off of her dick and sat back. "Maybe we should stop for now. You're looking a little flushed."

"I'm fine," said Twilight, blushing more. "Just a little hot. All the library windows are closed."

You weren't sweating during the last two hours we spent in here. Rainbow grinned again. "Want me to keep going?"

"Please," Twilight said, before slapping a hoof to her mouth.

"All right, then." Rainbow lay down on her back and let her rock-hard erection stand free. It wobbled a bit, and she felt some satisfaction as Twilight squeezed her legs together again. Rainbow reached her hooves up to her mouth, and one by one, spat on them. Then she took her hooves and put them back on her shaft, and began pumping them up and down.

Her pace was much faster, now. She began to breath heavily, stroking up and down and up and down. They glided over her saliva-dampened cock, going schlick schlick schlick. She felt a moan escape her, as her stallionhood twitched again.

It wouldn't be long, now. Rainbow was panting, furiously rubbing herself as she neared the finish line. She looked at Twilight, and found herself imagining her friend lying down with her legs spread out, pussy gaping wide to take Rainbow inside her. The unexpected image made her gasp in shock, and she felt an approaching wave of tension in her pelvis.

The wave crashed forward, and Rainbow felt herself pass the point of no return. "Twilight—I'm—oh!"

A fountain of white burst from the tip of her cock, arcing through the air. Rainbow shook as the tremors rocked her, sending shot after shot of hot, sticky cum flying. Her hooves kept pumping, and she rode her climax to the end, her chest heaving.

At last, the aftershocks began to fade. She opened her eyes and saw the trail of white across the floor, leading back to her dribbling cock. Rainbow panted, raising her head to see what Twilight was doing.

The unicorn was still staring at the stream of cum that Rainbow had shot across the wood. Her lips parted, and she said, "W-well, that should do nicely for the tissue sample. I'll just collect it..."

Her horn glowed, and an empty bottle rose in the air. The sticky liquid glowed purple, and it lifted off of the wood to pour into the bottle. Rainbow grinned. "Maybe I should keep you around for cleanup, Twi."

Twilight gave a shaky laugh. "I, uh, guess we should move on to the next one."

Rainbow watched as she started sorting through the bottles in the box. Twilight's tail was swishing back and forth in a nervous rhythm. Rainbow caught glimpses of something glistening beneath it. "Twi, you feeling okay?"

"J-just great!" Twilight smiled at her. "It's just a little strange seeing you with..."

"With a cock?" finished Rainbow.

Twilight blushed. "Yes."

Rainbow grinned. "Look, if you need a few minutes alone..."

"Rainbow!" Twilight's cheeks threatened to catch fire.

"What? I can't believe you're being modest after that. I just came all over your floor. If you're feeling a little... tense, just say so."

Twilight swallowed. "Okay, I admit it. That was really hot. I'm feeling very..."

"Horny?" Rainbow smirked.

"Yes," said Twilight, through clenched teeth. "Yes, I'm feeling ridiculously horny."

"Well, if you want, and you ask nicely, I can help you with that." Rainbow stood, and brushed past Twilight, flicking her with her tail.

Twilight looked shocked, but her protests seemed to get lost somewhere between her throat and her mouth. Her dry, thirsty-looking mouth. Rainbow rubbed past her side, raising her tail. "Tongue-tied, Twi?"

"You'd—you'd do that?" Twilight sounded half-excited, half-mortified.

"Sure! What are friends for? Besides," said Rainbow, rubbing her nose against Twilight's cutie mark and drawing a slight gasp of air, "I'm equipped for it."


	2. Chapter 2

Twilight didn't have to think about it for very long. Rainbow could practically smell the desperation on her. "Okay, Rainbow, but… please, let's keep this a secret, okay?"

"No problem." Rainbow nodded easily.

Fidgeting with anxiety both social and sexual, Twilight flicked her tail. "I'm a little nervous about this."

"Hey, relax. Let's head upstairs," said Rainbow, stretching her back. "The wood floor in here isn't super comfortable."

Rainbow followed Twilight up the library steps to reach her bedroom. There were books everywhere, of course, but right now Rainbow and Twilight had eyes only for the bed that lay beside the window.

Twilight sat down on the lavender sheets, and put her front hooves between her hind legs in involuntary modesty. "Okay, I'm really nervous about this."

Sliding a leg around Twilight's shoulder, Rainbow sat beside her on the bed. "Don't be. You need help, and I'd love to give it to you. There's nothing to be shy about."

"It's just…"

Rainbow raised an eyebrow. "Are you going to tell me you've never done this before?"

"No," said Twilight, blushing, "Though it has been a while. I'm just still a little weirded out by you being a—a stallion."

"Trust me, not half as weirded out as I am." Rainbow grinned. "But I think I'm starting to like it."

"But I mean—we're both mares, or we used to be. I don't know, it's confusing."

Rainbow shrugged. "If you'd rather I left…"

"No!" Twilight blushed. "I… I want you to help me."

"To help you what?" asked Rainbow, smiling coyly. She traced a hoof in a slow circle on Twilight's chest.

"You kn-know." Twilight's cheeks were back to imitating a tomato.

"Say it for me," Rainbow whispered into her ear. "You want me to help you…"

"C-cum," stammered Twilight. "I want you to help me cum."

"Well then," said Rainbow loudly, "Let's get to it. How do you want to do this? Hoof? Tongue? Or should I give my new appendage a test drive?"

"Let's start with hoof," said Twilight, with a swallow.

"Oh, Twi," said Rainbow, half-smiling, "You don't need my help for that." She reached down and grasped one of Twilight's hooves. Lifting it up, she pressed it to Twilight's chest fur and began massaging it.

Rainbow reached back around Twilight, and pulled her over slowly, to lay on her back. "You just take your hoof, and pull it down…"

She moved Twilight's other foreleg aside, and got her first glimpse of Twilight's hidden treasure. The unicorn's lavender folds were flushed pink with arousal, spread like a blooming flower. Dew glistened on the petals, and Rainbow inhaled the scent of mixed sweat, desire, and something that was uniquely Twilight.

Rainbow pulled Twilight's hoof down her belly. She guided it into the trench, sliding it through the damp slit. Twilight, looking down at it, shivered.

Beginning to pull the unicorn's hoof back and forth, Rainbow leaned over and whispered, "See? It's not hard. You just move up and down, up and down…"

Twilight's lips parted, and she gave a tiny moan. "Faster."

Moving Twilight's hoof aside, Rainbow pressed her own to Twilight's nether lips, and began sliding it to and fro. Twilight's breathing was growing deeper. Rainbow rubbed slowly and then quickly, alternating her speed and drawing a little gasp whenever she surged upward.

"Of course, hooves are kind of big, and clumsy. If you really want to scratch that itch, you're going to have to get… delicate." Still massaging Twilight's pussy, Rainbow sat at the foot of the bed and stuck out her tongue. She touched it to Twilight's left ankle, and ran it up the inside of her leg.

"Oh, Rainbow…" Twilight closed her eyes.

Continuing to draw her tongue across Twilight's inner thigh, Rainbow lifted her now-damp hoof and began massaging the opposite leg. She ran her tongue up to the line where Twilight's leg met her pelvis.

The smell of Twilight's pussy was strong and intoxicating. Rainbow wanted to dive in right now, but forced herself to be patient. Between her own legs, she could feel that her cock had fully hardened again, ready to go for round two. Not yet, she thought, drawing her tongue down to the spot beneath Twilight's slit and holding it there. Still, lying on her stomach, she began grinding her dick against the sheets, enjoying the friction.

Twilight moaned. "Rainbow, please…"

Rainbow's tongue danced up, finally meeting the wet, fragrant folds of Twilight's pussy. She pushed inside, drawing a deep groan from the unicorn. The warm walls pressed against her tongue as she explored, seeking the bumps and inner folds that drew squeals of pleasure from Twilight.

She felt her head squeezed on either side as Twilight brought her legs together. The unicorn put a hoof on Rainbow's head and murmured, "Deeper."

Her tongue pushed further in, savoring the sweetness of her friend. Twilight tasted as unique as she smelled, but Rainbow thought she recognized a slight rose-petal aroma from the unicorn's bath soap. Smiling, she tongued deeper into Twilight's pussy, enjoying her reactions to the licking.

Twilight was squirming with every lap of the tongue, and her moans had become near constant. "Th-that's so g-good, Rainb-b-b-b-aaaah." She dug a hoof into the bedsheets and pulled them up to her head. Her teeth were clenched tightly with pleasure.

Rainbow slowly withdrew her tongue from inside Twilight, and lapped up the juices dripping from her pussy. They were sweet, like fruit; maybe it was a side-effect of doing all that magic. Rainbow focused on her prize, the tiny button poking out from under its hood at the top of Twilight's lips.

She touched it with the tip of her tongue, and Twilight gasped. Casting a glance up, Rainbow asked, "Too sensitive?"

"N-no," panted Twilight, her chest heaving with shallow breaths, "M-more, please."

Rainbow grinned and licked Twilight's clit again. The unicorn writhed under her attentions, shuddering with pleasure. Curling her tongue, Rainbow rolled it around Twilight's most sensitive spot, and Twilight let out a deep groan from the back of her throat. "R-Rainbow Dash, that's…"

Her grinding motions had been intensifying without her notice. Rainbow realized she was dangerously close to finishing herself, and slowed her pelvis. Her cock was swollen and aching, but she imagined that Twilight was in even more delicious distress.

She suckled Twilight's clit like a foal hungry for milk, making Twilight twist and turn in exquisite agony. As she felt Twilight tense beneath her, Rainbow suddenly let go, pulling away, watching with satisfaction as a strand of drool stretched between the tip of her tongue and Twilight's dripping slit.

Twilight raised her head, distressed. "Wh-what's wrong?" Her chest was heaving. Rainbow could nearly taste her frustration.

"Sorry, Twilight," said Rainbow, her voice low and husky, "but I don't want to make a mess of your sheets. I'm ready to burst over here."

Me, too! she imagined Twilight screaming in her head. Twilight gave an adorable whine of frustration. "Rainbow!"

"Just give me a second to cool off," said Rainbow, grinning at Twilight's clear desperation.

"Forget cooling down. If you're worried about making a mess—" Twilight swallowed, but her craving for release pushed her forward. "Do it inside me."

Rainbow jolted in surprise. She hadn't been expecting that, not so soon. "For real?"

"Do it." Twilight rolled over onto her stomach. She stuck her curved, beautiful little butt into the air, and swished her tail out of the way. "I want to see how you feel."

Well, I'm not going to argue. Without wasting another moment, Rainbow scrambled up behind her. She leaned down over Twilight's rump and tried to calm her breathing. Twilight's pussy was soaked from her earlier ministrations, and she could see the hole just waiting for her. It was spread with Twilight's legs, shining wetly.

Rainbow straddled Twilight, reaching a hoof down to feel her cock. It was harder than before, and it twitched at her touch. She inhaled, preparing herself. She guided the tip of her cock down to meet Twilight's hole, pressing up against it.

Twilight groaned into her pillow. "Please, Rainbow. I want it."

"Y-yeah," said Rainbow, her confident façade shaken by the burning in her loins. She pushed forward, sliding into Twilight's pussy, and let out a low ohhh.

As she burrowed deeper inside, she felt the warmth of Twilight's natural lubricant surrounding her cock. The walls of Twilight's pussy clenched against her, and Rainbow grunted. To her satisfaction, she could fit entirely inside Twilight, her balls finally touching the unicorn's skin.

"Wow…" Twilight's eyes were rolled back into her head. "This is… Rainbow, I feel so full. It's like…"

Rainbow leaned over Twilight's back, still buried inside her. She nuzzled up against the back of Twilight's neck. "It's like we're one pony."

"Mmm." Twilight squeezed her, and Rainbow blew out a breath. "Please, Rainbow."

Rainbow moved, and discovered that it could get better. The friction of the sheets was nothing compared to the hot, wet sliding sensations she felt as she glided into and out of Twilight's wonderful pussy.

The ring around her cock drew a gasp from Twilight every time it passed inside her entrance. Twilight, in turn, opened up when Rainbow pushed forward and squeezed when she pulled out, a sensuous, incredibly erotic motion that drove Rainbow wild. She plunged into Twilight with increasing fervor, shockwaves of pleasure surging through her with each thrust.

She opened her mouth and bit down gently on Twilight's ear. Beneath her, Twilight wriggled in ecstasy, moaning and panting as Rainbow filled her again and again. Rainbow nibbled on her ear again, drawing more noises of delight that made her cock spasm inside Twilight's depths.

"How's it feel, Twilight?" she whispered, increasing her speed.

"S-so good, so good, so good," breathed Twilight, unable to form more coherent sentences.

"I'm nearly there, Twi." Rainbow let out a low, sultry growl. "Tell me what you want."

"I want—" Twilight jerked into her pillow as Rainbow pushed into her slick passage again. "I want—I want—"

Rainbow could feel it in the distance, approaching, inevitable, but not yet upon her. She whispered, "Tell me. Tell me what you want."

"I want—" Twilight screamed into her pillow, as Rainbow's balls slapped against the tiny button of her clit over and over. "I want you to cum inside me. Cum in me, Rainbow! Fill me up! Please!"

Fireworks were going off inside her head. Rainbow lost all control as her orgasm hit her like a stampeding buffalo. She plunged as deep as she could go into Twilight, holding there as her cock pulsed. The heat inside was suddenly intensified as her first spurts came out. Rainbow held on, riding the tide of pleasure.

A cry ripped itself from her throat as she surged again, and felt her sticky seed flowing past her cock as it began to fill the space between her and Twilight. She quivered again as another blast rocked her to her core. Cum leaked around the sides of Twilight's pussy, hanging from the bottom of Rainbow's cock. She stayed inside Twilight, slowly regaining control of her breathing as the earthquake of bliss began to fade.

Twilight squeezed her, forcing more cum out around Rainbow's cock. "Just a little more, Rainbow!"

Rainbow was still dribbling inside Twilight, but she knew just what to do. She pressed close against her friend's rear, and began rubbing her balls against Twilight's clitoris. Twilight threw her head down into the pillow and let out a cry of absolute joy, and then her hips began to shake. She shuddered, squeezing Rainbow's cock as if desperate to get every last drop out. Warm liquid that was clearly not Rainbow's cum squirted out from the top of Twilight's pussy, coating Rainbow's balls.

Twilight's orgasm lasted longer than Rainbow's. Thirty seconds had passed before she stopped shaking, and another ten before she slumped to the bed. Rainbow slowly pulled out of her, watching as a small flood of cum and pussy juice ran out after her. Strands of it stretched between the tip of her cock and Twilight's entrance, while gobs of it dripped from both of them onto the bed.

Rainbow flopped down beside Twilight, resting her head on the pillow. "Looks like we made a mess, after all."

Twilight shook her head, still speechless. She waved a hoof. "I'll put the sheets in the laundry." She turned to Rainbow, glowing with post-coital relaxation. "Thank you, Rainbow. That was… I don't even know."

"You can't think of a word?" Rainbow grinned. "I guess I must be good."

"Very," said Twilight dreamily. "I haven't cum that hard in…" She sighed with delight and closed her eyes.

Rainbow looked down at her softening dick, still covered with sticky white semen. "I think I can do you one better."

Twilight opened her eyes. "Are you serious? That was unbeatable."

"Yeah, that's what I thought, until I did it with this." Rainbow rubbed her cock, and it jerked under her touch. She grinned at Twilight. "You have to try this out."

Twilight stared at Rainbow's cum-soaked cock, and a faint smile played at the edges of her mouth. "Let's go get that box of potions."


	3. Chapter 3

Twilight was still oozing, so they elected to send Rainbow alone. She made her way downstairs, still flushed with the heat of sex, and filled with anticipation of what was to come. No pun intended, she thought with a grin.

She found the boxes standing untouched on the table. Rainbow looked through the list that Twilight had left beside them, smiling with success as she found the one she was looking for. Bottle sixty-four, 'Mare Malt,' tasted like strawberries. Rainbow felt her face beginning to change first, wrenching back to its earlier form. Her legs were next, abruptly shortening and thinning. Her hindquarters jerked forward, and after running a hoof along them, Rainbow discovered that her familiar athletic curves had returned.

The last to go was her wonderful dick. It had already retreated back into its sheath, but she felt a very odd sensation as it shot back inside her, and vanished. Looking down, she was met with the familiar sight of her blue-lipped slit. A quick inspection of the pink interior of her folds assured her that all was well.

She gave herself a friendly rub. "Hello again!" She patted her pussy, comforted to be back in her own body; though she had to admit she was going to miss some things about being a stallion.

Lifting the box of alteration potions onto her back, she stepped daintily off toward the stairs. She climbed quickly and surely, keeping the box carefully balanced. The bottles clinked together as she ascended. She pushed back into the room, smiling.

Twilight was still on the bed, her legs spread to allow herself to drain. At Rainbow's entrance, she looked up and beamed. "Got it?"

"Yup. Breakfast in bed." Rainbow set the box down by the door and lifted out the bottle of 'Stallion Sherbert.' She uncorked the potion, and offered it. Twilight's horn glowed, and the bottle drifted through the air to her. She drank from it, then recorked the bottle and floated it back over to the potion box.

Twilight's face scrunched up. "Oh, that's... this is really strange." As Rainbow watched, Twilight's muzzle shot out, turning blocky. Rapidly, her body changed, transforming the little unicorn mare into a handsome young stallion.

Not under the duress of transformation herself, Rainbow got a clear look at Twilight's crotch as her pussy glowed with magical light. A dark purple shaft erupted from within, showering the bed with all the leftover cum that had lain inside. A hanging sack followed, and then Twilight's delicious honeypot had vanished, replaced by something Rainbow was very much looking forward to investigating.

"How's it feel?" she asked, sliding onto the bed.

Twilight prodded her new cock. The deep violet was speckled with lavender at its base, but Rainbow had the feeling it was going to be painted white soon enough. Twilight blinked. "It's, uh... interesting," she said, her voice half an octave deeper than normal. Rainbow found the new timbre enticing. "It's so sensitive..."

"Isn't it great? It's like a foot-long clit." She surreptitiously rubbed her own on the bedsheets. "Ah... okay, maybe not quite that good." The sheets where she had rubbed were tellingly moist. Rainbow licked her lips in anticipation.

Twilight stood on the bed, and bounced. "Let's try it out!"

"Not so fast, Twi," said Rainbow with a grin. "I got a warmup, first. It's only fair to give you the same."

"Oh. You mean I should, um, play with it?"

"No." Rainbow gestured down to the bed, the foot of which was still very damp from their earlier pleasure.

"Okay..." Twilight sat down, spreading her legs to allow Rainbow better access. "But what did you have in muh-muh-miiinnd... ohhh..."

Rainbow had brought her wings forward around her, and brushed against the tip of Twilight's stiffening cock. She traced the feathers up and down Twilight's length, watching her shaft twitch with little jolts of excitement whenever she touched it.

Her wingwork had always been a point of pride. Not all pegasi were as dextrous with theirs as Rainbow Dash, but she'd worked hard to master her wings so that she could in turn master the tiniest currents of air in the skies. The currents of heat running through her at the moment were equally wonderful, however.

She drew her left wing up the bottom of Twilight's cock, while sending her right lower to tickle the unicorn's balls. Twilight squirmed. "Wow, those are touchy." She grinned. "Keep touching."

Rainbow happily obliged, drawing her feathery touch along the bottom of Twilight's sack. She made sure to brush Twilight's inner thighs, drawing a gratifying rumble from her friend's throat.

Twilight inhaled slowly. She ran her tongue along her top lip. "I can smell you, you know..."

Rainbow laughed weakly. She was so wet that she could actually hear a faint squishing sound whenever she moved on the sheets, and restraining herself from just jumping onto Twilight's cock was becoming difficult. She continued the massage with her right wing, but brought the left one up to her mouth, and bit the tip.

"You're doing that again," noted Twilight with a little groan of satisfaction.

Rainbow released her wing with a sheepish grin. "Pegasus wings aren't overly sensitive, but just a little nip on the tip..."

Twilight beckoned, and Rainbow extended her wing. Twilight placed the tip in her mouth and bit down gently. Rainbow drew a sharp breath in through her teeth.

Determined not to be one-upped, she lay down flat on her stomach, and licked the flattened head of Twilight's cock. In response, Twilight bit down a little harder. She placed her hooves on Rainbow's back, between her shoulder blades, and began massaging them.

No longer caring that her ever-wetter pussy was staining the sheets, Rainbow began running her tongue along Twilight's length. She lingered at the top, tracing the head with saliva.

Twilight continued massaging her, alternating nibbles between her left and right wingtips. Rainbow dropped low, and caressed Twilight's balls. She could detect the slight tang of the cum that had coated Twilight's pussy before the transformation.

Twilight reached over her, and put her hooves on Rainbow's rump. She pulled Rainbow forward, dragging her slit across the sheets and drawing a muted squeak.

"Feeling a little flustered, are you?" Twilight rubbed her between the wings, and Rainbow melted. "Serves you right, for not finishing me earlier."

Struggling not to roll over and simply let Twilight massage her to climax, Rainbow's mouth curled. "I won't make that mistake again." She wrapped her mouth around the tip of Twilight's cock, and felt her go rigid.

Rainbow started sliding down the length of it, wondering how deep she could go. Twilight's hooves had slowed on her back, shocked out of their rhythm. They stopped altogether as Rainbow went farther.

She made it about three quarters of the way down before she finally found her limit. This was going too well for her to test her gag reflexes, so Rainbow eased off. She drew back over the ring at the middle of Twilight's length. As her lips passed it, she began sucking on Twilight's cock like a milk bottle.

Twilight hissed with pleasure, and placed her hooves on Rainbow's flanks, right over her cutie marks. She began rubbing them in circles, her gentle touch clouding Rainbow's head with fire and smoke. The bed beneath her felt like a wet rag by now. She slid her hoof down under her stomach, unable to hold back any longer. Rainbow fondled her pussy, moaning as she sucked away.

Her dripping folds burned as she drove her hoof into them. She stuck her tongue under Twilight's cock and started sucking up and down, waiting for the inevitable explosion. Twilight began thrusting in time with the bobs of her head, groaning.

Rainbow slid all the way back, leaving only Twilight's tip in her mouth. She slathered the head with her tongue, looking up at Twilight with lidded eyes.

Her only warning was a grunt from Twilight. The unicorn's cock burst in her mouth, flooding it with a startling amount of cum. Rainbow did her best to hold it all, but there was so much. It leaked around her lips, and splashed out as the last spurt surged.

She held on as Twilight thrusted a few times. Taking a deep breath through her nose, Rainbow curled her tongue along the head of Twilight's cock to roll up the last few drops, and swallowed. It went down her throat, hot and sticky, and she gave a satisfied ahhh.

Twilight fell onto her back. "Mmm." She lifted a hoof as if about to say something, then let it drop.

Rainbow clenched her teeth. Twilight was falling into afterglow-mode, but the burning in her own loins had reached a fever pitch. "We're not done yet!" She drew her hoof out from beneath her, and placed it plaintively on Twilight's thigh. Rainbow was completely soaked and totally desperate; she regretted making Twilight wait so long earlier.

Twilight just mumbled something happily. Rainbow gave a low whine. "Hurry up!" Hoping to jump-start her friend, she started lapping at Twilight's softened cock.

From the other side of the bed, Twilight whispered something. Rainbow looked up. "What?"

"Wings!"

Rainbow quickly stretched her wings in front of her to start another feathery wingjob. Twilight gave a happy moan, and her purple shaft flopped briefly up. With a delicate touch, Rainbow teased her, baiting Twilight's cock back to stiffness.

Unable to hold back any longer, she rose and crawled on top of Twilight. She rubbed her pussy against Twilight's hardening stallionhood, closing her eyes as she felt her moist heat against the velvety soft skin.

Twilight lifted her head and whispered, "Kiss me."

"Finally," said Rainbow, plunging down into Twilight's mouth. Their tongues twisted together, greedily seeking each other. Rainbow pushed her head forward, her lips locked firmly with Twilight's.

Below, she felt Twilight spread her legs apart, readying her for penetration. Rainbow's eyes rolled back as she felt Twilight slide into her at last. Twilight devoured Rainbow, her tongue seeking and prodding inside the pegasus's mouth. Slowly, she pushed inward, with her tongue and her cock.

Rainbow waited until Twilight was fully inside her. As soon as she felt the soft squish of Twilight's balls beneath her butt, she pulled away from the kiss. She felt a little drool coming out of her mouth, and wiped it with a hoof and an embarrassed grin.

She began slowly gyrating, twisting her hips around in a circle. The huge shaft inside her was a delight, a sensation of fullness she hadn't had in far too long. Rainbow rocked back and forth, enjoying the tugs and pulls inside her pussy.

Twilight groaned, and Rainbow took that as her cue. Placing her forelegs on either side of Twilight to steady herself, she began gliding up and down on Twilight's cock, glorying in the wet slaps as the lower folds of her pussy hit Twilight's balls on every downward push.

It felt as though she were walking along the edge of a cliff, looking down, daring herself to jump, and not pull out until the very last moment. Rainbow pushed closer to the edge, sweating and panting and groaning and moaning, stretching for release.

Twilight's horn glowed, and Rainbow felt her wings pulled gently forward. They stretched before her to meet, their tips touching just above Twilight's muzzle. Twilight opened her mouth, took the wingtips inside, and bit down.

Rainbow fell from the cliff. Her pelvic muscles seized up, and she felt a hot wave radiate out from her core. She thought she might be screaming, but she couldn't tell over the pounding in her ears. Her body quaked all over as she came, a whirlpool of ecstasy draining out through her pussy. She rode it out, her hips shuddering with every pleasurable pulse.

Unlike Twilight, Rainbow was not a squirter; but it didn't matter. Her convulsions were enough to set off Twilight herself. Rainbow felt Twilight's balls clench up beneath her, and suddenly her pussy was filled with a boiling, sticky mess. Twilight groaned over and over as she pumped her cum out and into the damp space inside Rainbow.

As the spasms faded, Rainbow lay down on top of her, her mind totally blank. Twilight nuzzled her. "You were right, Rainbow... That was even better than the last one."

"Told... you..." Rainbow sighed, her mind completely shattered. "I'm good."

Her senses slowly began to return, and she lifted herself off of Twilight, leaving a sticky puddle on the increasingly-messy bedsheets. She kissed Twilight's chest, then grinned as an idea slithered its way into her mind. "I'll be right back."


	4. Chapter 4

She slid off of the bed, finding her hooves unsteadily. Pressing her front right hoof between her still-shaking legs to keep from dripping onto Twilight's floor, she wobbled on three legs across the room to the box of potions.

Twilight, lying in a cloud of bliss, rolled her head over to look at Rainbow. "Switching again? All right..." She blew a sweaty strand of her mane out of her eyes. "Could you bring me the mare potion? I don't even know if I can stand right now."

"Gimme a second." Rainbow downed the potion, smacking her lips.

"Huh?" Twilight blinked.

Rainbow felt the transformation beginning. She gritted her teeth as the stretching came upon her again. Her body blocked out, and the hoof pressed to her nethers was suddenly shoved forward, and given a coating of leftover fluids that splattered around it onto the floor. Whoops. Forgot about that.

"I'll get that later," she muttered sheepishly, turning back to Twilight and grinning.

Twilight smirked. "There's a bottle of 'Varnish Vanish' in one of the boxes. 'For the really tough stains,' Zecora said." She tilted her head against the sheets. "So are you bringing me that mare potion or not?"

"Nope." Rainbow's grin widened.

Twilight frowned in confusion, before a glimmer of understanding lit in her eyes. She raised herself off the bed, sitting up on her haunches. "You sure about this?"

"Oh, come on, Twilight! When are we going to get another chance like this?" Rainbow raised an eyebrow in what she hoped was a seductive look. They might acquire more potion, of course, but she was unsure that they would ever both be willing to go this far again once their heads had cleared.

"I..." Twilight laughed, and shook her head, still processing the idea. "You've got a point, I suppose. And hey, we should test this potion thoroughly." Her eyes narrowed, and her smile sharpened. "But this time, I want to be on top."

Rainbow swallowed. It had been a long time since she'd tried this sort of thing, but like she'd said, when was an opportunity like this going to come along again? "Deal."

Twilight scooted back on the bed to make room, but Rainbow turned back to scan the list of potions. Clearing her throat, Twilight asked, "Something wrong?"

"While you're already pretty, ah, slippery," said Rainbow, giving a little aha as she found something promising, "I'll feel better if you have some assistance."

Rummaging in the box, she withdrew another bottle, this one unopened. "Here we go. Number seventy-two, 'Sugar Glider Glide.' This ought to do the trick."

Twilight gave an un-stallionlike giggle. "Zecora told me she uses that to lube her door hinges."

Rainbow grabbed the bottle in her mouth and grinned as she carried it over to the bed. She set it down on the damp sheets. "You believe her?"

"Not anymore." Twilight's horn glowed, and the bottle floated over to her. Rainbow slid onto the bed, as Twilight popped the cork and started rubbing the bottle's contents on her rising stallionhood. "Mmm, smells like vanilla."

Rainbow slid across the sheets, feeling her leg touch a sticky patch. She stuck her tongue out. "I am going to need a long bath after this." She gave Twilight a skeptical look. "You still got another one in you?"

"Oh, yes," murmured Twilight. Her dick was now shining with a coat of neatly applied lubricant. She recorked the bottle, and set it on her nightstand. "Now, if you don't mind," her eyes glinted, "let me see those pert little cheeks of yours."

Swallowing her doubts, Rainbow twisted over on the sheets and bent down. She raised her rear, and felt a slight air current tease the rigid cock hanging between her legs. Flicking her tail aside, she spread her legs slightly to allow better access. Rainbow took a deep breath, and blew it out slowly.

Twilight's weight shifted behind her on the bed. Purple hooves touched the sheets to either side of her, and she felt a warm body press against hers. Unexpectedly, the first contact wasn't on her hindquarters. She felt Twilight's shaft sliding along underneath her own, slipping smoothly past her balls and rubbing the length of her dick. She gave a short, surprised grunt.

Twilight began slowly grinding under her. Rainbow closed her eyes and tried not to pant. She felt painfully hard again, but totally conflicted between the desire to plunge into something or have herself filled.

Twilight withdrew from beneath her, and then Rainbow felt a hard rod sliding between her buttcheeks like they were sandwich buns. Twilight rocked back and forth, sawing her cock on Rainbow's backside.

Rainbow was panting hard, now. "I'm ready, Twi."

"Okay," said Twilight, giving her flank a comforting rub. Rainbow felt something warm spill over her backside, and guessed that Twilight was pouring more 'Sugar Glider' over her. She wiggled her backside in anticipation.

Finally, she felt the head of Twilight's cock at her rear entrance. It entered her slowly, unstoppably, and she felt a low purr in her throat as it pushed inside. Her own dick jerked up with tension, but she held herself still as Twilight went further.

"This is... a lot tighter," grunted Twilight, her hooves firmly planted on Rainbow's cheeks.

"Tell me about it," said Rainbow, her lips dry. "Keep going." She stared down at the rumpled sheets and her own twitching cock as Twilight pressed deeper, inch by inch.

Rainbow felt an unmistakable soft feeling, as Twilight's balls squished up against the region between her butt and her own sack. Her cock was aching for release, now, and she flipped her tail up over her back. "Come on, Twilight." She looked over her shoulder and panted, too desperate with desire to even smile. "Rut me."

Twilight began to move, and the real delight began. The unicorn slid in and out of her butt, making Rainbow groan with every filling thrust. Her cock slapped up against her belly as her hips rocked, sending little bolts of pleasure up her spine. A trickle of lubricant slid down her leg.

Shoving all the way forward, Twilight leaned down over Rainbow's back, and whispered in her ear, "I have to say, Rainbow, I love this. Being this deep inside you, it's..." she grunted, and thrust again, "it's just..." She shook her head, and gave up trying to find the word.

She placed her hooves on Rainbow's back, and pushed her down to lie flat on the bed. Rainbow's cock was pressed between her belly and the sheets, still throbbing. Not leaving her, Twilight continued to pound away, getting faster and harder with every stroke.

Rainbow felt herself drooling as each slam in her butt pushed her cock over the sheets, rubbing it against her belly. Her legs felt boneless as she let Twilight ram her again and again. "S-s-so f-full..."

Suddenly, as Twilight shoved inside her, she felt a shattering blast of incredible pleasure. She choked with surprise, her eyes crossing. Twilight paused. "You okay?"

"Y-yeah." Her chest heaved. "Wow. That was as good as having my clit tweaked. D-do... hit that spot again."

"I can try." Twilight pulled nearly all the way out, leaving a mere half-inch inside, before slamming her entire length home.

Rainbow squealed as another wave shook her, and her balls squashed against the bed. "Ohhh, Twilight, I don't think I can take another one of those."

"Let's test that, hm?" Twilight squeezed Rainbow's flanks together and buried herself inside. Her cock hit that glorious region again, and Rainbow lost all semblance of control.

Her cock erupted beneath her, smearing jets of cum into the sheets and her sweaty fur. She gave one long, continuous moan as she came, shuddering as she pumped out her load.

Twilight slowed her thrusts, and slowly slid out of her. She gave a little huff. "Aw, done already?"

Rainbow rolled out of the huge wet spot she'd created, not that the rest of the bed was in much better shape. "Sorry, Twi," she said weakly. "That was just too much for me. Too good, too fast."

"Hmm." Twilight eyed her cum-soaked fur with a mischeivous gleam in her eye. She smiled. "I've got a hypothesis I'd like to test."

"Oh?" Rainbow blinked, still recovering from her powerful climax.

"I'm wondering if drinking the stallion potion again has, er, 'reset' you, so to speak." Twilight poked Rainbow's limp cock.

"Think I have more in me?" Rainbow laid her head back on one of the pillows, the sole completely dry spots left. "Feel free to try, but I don't think you're gonna have any luck."

"We'll see." Twilight placed a hoof on Rainbow's dick and began slowly massaging it.

Rainbow smiled. "It feels nice, but not hard nice."

Twilight merely leaned her head down and stuck out her tongue. Rainbow raised an eyebrow. Surely she's not thinking of—

Rainbow's breath caught in her throat as Twilight touched her balls with the tip of her tongue. Twilight ran up along the length of Rainbow's shaft, but she didn't stop at the tip. She kept on going, her tongue pushing through the cum-soaked fur on her belly. Finally lifting off, Twilight swallowed, and licked her lips.

"D-dang, Twi..." Rainbow took a shaky breath as Twilight began giving her entire belly a tongue bath. She let her head fall back into the pillow and let go, enjoying the sensation of Twilight's tongue lapping against her soft, tender skin.

For at least a minute and a half, Twilight continued her work, cleaning Rainbow's lower half from the top down. Soon, Rainbow felt a now-familiar feeling as her loins reported in for duty. "Ah, Twilight... about that reset thing. I think you were right."

Twilight smiled. "I often am." She continued licking, finally reaching Rainbow's cock. She rolled her tongue around it, taking dollops of the sticky semen like she was eating ice cream. With agonizing slowness, she cleaned the last of it, sucking on Rainbow's tip and drawing a groan.

She sat back, clearly satisfied with her work. "Ready to keep going?"

"Ye-yeah." Rainbow propped herself up.

"Excellent." Twilight sighed, smiling ruefully. "All right, I had my turn." She levitated the bottle of lube over again, and unstopped it. She poured the liquid over Rainbow's stiff erection like syrup on a pancake. It was warm and runny, dripping over Rainbow's entire crotch and soaking down into the sheets.

Rainbow shifted her balance, spreading her legs to give her cock a clear path up. Twilight rose above her on all fours, and slowly lowered her butt down onto Rainbow's waiting dick.

As Rainbow felt herself entering, Twilight's eyes widened. "Wow," she muttered, "That's... different."

She let herself slide down slowly, but slipped and suddenly rammed down on Rainbow's cock. Both of them gasped with surprise. Twilight winced. "Ow."

"You okay?"

"I think so. Just give me a minute to get used to this."

Rainbow smiled amiably, and looked down at the long, purple cock now lying on her chest. She stretched her right wing around and began gently massaging it. Twilight hummed in enjoyment.

Twilight's dick lifted as she pushed herself up. Slowly but surely, she began riding Rainbow, gliding up and down on the pegasus's lubed-up shaft. Her face was glowing with suffused heat and pleasure, pushing herself toward one more orgasm.

It wouldn't be long. Both of them had already had a crazy number of climaxes today; Rainbow knew Twilight had to be burning fumes. The unicorn's mouth made a little o as she rose and fell, her cock slapping against Rainbow's chest with every descent.

Twilight gasped again, now moving as hard and fast as a jackhammer. The next time she came down, Rainbow grabbed her flanks and squeezed like Twilight had done earlier, jamming herself as deep in Twilight's butt as she could go. Twilight's eyes shot wide open, and her mouth hung loose. "Oh-"

Her cock blew like a volcano, hosing Rainbow in the face. Thankfully, the blast missed her eyes, leaving a thick, sticky line across her mane, nose, and mouth. The second and third shots fell short, landing on her chest. Twilight kept going, her eyes rolling up into her head.

Rainbow ran her tongue around her lips, licking up the strands that lay across them. The tangy taste was enough to finish her off, and she closed her eyes as she felt the rush begin again. Her hips bucked up as she burst inside Twilight, filling the unicorn with a boiling splash.

Twilight didn't wait to pull off. Rainbow's cock flopped to her chest, completely spent. With cum oozing from her butt, Twilight slowly ground her softening dick against Rainbow's. Their cocks both moved limply, still dribbling. Their cum pooled together on Rainbow's chest.

"I see... what you meant..." panted Twilight, "about that spot." She blew out a breath.

Rainbow touched her chest and lifted a sticky hoof. "It's kind of a shame. You worked so hard cleaning me..."

Twilight grinned, and her horn glowed. All of the cum matting Rainbow's fur suddenly slid off of her, into the demolished bedspread. Rainbow's mouth worked wordlessly for a moment. "You mean you could have done that in the first place?"

"Sure," said Twilight, laying down beside her. Twilight ran a hoof softly in circles over Rainbow's chest. "But I think the first way was more fun."

Rainbow gave an exhausted laugh. "I never knew about this side of you, Twi."

"You know me pretty well now. Inside and out." Twilight kissed her neck.

"Yeah." Rainbow twisted to cuddle, feeling her still-softening dick brush against Twilight's. She purred in satisfaction.

"Mmm," mumbled Twilight. "I suppose we should change back. I've got to get these sheets cleaned before they're permanently ruined."

Rainbow snorted. "You might just want to burn them." She nuzzled Twilight's neck. "Besides, we've got one thing to do first."

"Hmm?"

"There's still a matchup we haven't tried."

Twilight gave a throaty murmur. "Well, we don't want our experiment to be incomplete, do we?"

Rainbow kissed her on the cheek. "Definitely not."


	5. Chapter 5

Rainbow hobbled out of the bed, her legs weak. She made her way across the room to the box, and found the mare transformation potion right where she'd left it. Bringing it back over, she rolled into the sheets beside Twilight and handed her the bottle.

While Twilight drank, Rainbow gave a relaxed sigh. She wasn't sure how the day could get better, but she was willing to give it a shot.

"Here you go," said Twilight, her voice returned to normal. Rainbow took the bottle and sipped from it. Soon the transformation hit her, and she grunted as her body shrank back to its original form.

She set the bottle on the nightstand, and then turned back to Twilight. "So, what now?"

Twilight grinned. "You've had a sampling of all the available dishes. I'd like to get a taste."

Rainbow nodded. "Okay," she said with a small smile, "but I'm thirsty, too." She crawled down the bed, where she swung her leg up and over Twilight, straddling her face. Before her, Twilight's legs spread to reveal her tail and her wonderful little privates. Rainbow rubbed them with her nose.

Between her own legs, Rainbow felt a soft, wet touch on her slit. She was a little surprised that she could even get aroused at this point, but after another few licks she was wetter than Twilight's tongue alone could account for. Twilight leaned up and pressed her tongue firmly at the bottom of Rainbow's pussy, and she felt a hot, slick sensation as it burrowed inside her.

Humming with delight, she began licking Twilight. Her tongue ran between the unicorn's velvety folds. She could taste Twilight's arousal. Her nose was filled with the sweet scent of it, and she felt her own loins grow hotter.

Rainbow felt Twilight's tongue exploring deeper. She purred as it rubbed over ridges and bumps, wiggling up and down. It wasn't as filling as a dick, but it was much gentler. Rainbow closed her eyes and thrust her tongue inside Twilight.

Beneath her, Twilight put her hooves on Rainbow's flanks and pulled them down onto her face. She kept tonguing Rainbow, flicking in and out of her ever-wetter pussy. Rainbow returned the motion, trying to see if she could reach the end of Twilight's tunnel. Her tongue wasn't long enough, but as she thrust it deeper inside, Twilight began grinding up against her muzzle.

Their pace was measured, almost leisurely. They were both tired from the exertion of so many climaxes, so they were willing to let these last ones come in their own time. Rainbow and Twilight licked and sucked and prodded in slow, tender motions. Rainbow felt a new sense of enjoyment as she realized that they were finally pleasuring each other in their true bodies. It felt more personal, somehow.

Twilight's tail began swishing back and forth in an involuntary rhythm. It tickled Rainbow's nose, drawing a smile. Rainbow pushed her tongue up against the bottom of Twilight's pussy, and slowly drew it out like she was licking the side of a popsicle.

Twilight shuddered beneath her, but it wasn't yet the telltale pre-climax shake that Rainbow had come to expect. Actually, she was starting to think she'd hit that state before Twilight; the tongue inside her was taking her breath away.

Deciding this was one contest she could lose, Rainbow began idly running her tongue in a tall oval around the outside of Twilight's pussy. It brushed against her clit on every pass, drawing a little squeak. Below her, Twilight's tongue was slipping in and out of her like it had Sugar Glider poured on it.

It felt like she was climbing a huge hill, a rising sense of feathery height gradually filling her up. Rainbow slowly lathered saliva on Twilight's clit, watching her tail flick with every rub. She heard a moan from beneath her, and grazed the button with her upper teeth. Twilight tensed, and then Rainbow felt the tongue leave her.

Twilight began teasing Rainbow's clit in turn, drawing labored breaths. Rainbow gently rocked her hips back and forth over Twilight's mouth, reveling in the slow, measured strokes of her tongue. She was close to the peak of the hill, her entire body felt suffused with heat. Pressure built inside her loins, a bubble of pleasure just waiting to pop.

She crested the hill at last, and the bubble burst. Rainbow came soft and slow, with a wordless noise of happiness buzzing in her throat. Her pelvis gently ground against Twilight's mouth. Twilight's tongue lapped at her dripping folds, guiding her down from her climax like a warm, wet beacon.

Rainbow cooed with delight, and slumped. Twilight leaned her head back on the pillow to get comfortable, and rubbed her hoof on Rainbow's flank.

Only one thing left to do. Twilight's pussy was, to put it mildly, moist. Rainbow dived back into the soaking slit, reveling in the flavor. Twilight squirmed as Rainbow licked her, and clenched her butt. It was the little things that made the sight so arousing; the way she twitched when Rainbow's tongue hit just the right spot inside her, the sticky droplets of white caught in her tail, the shiny patches in her fur where the Sugar Glider and Twilight's own, natural lubricant mixed.

Rainbow pulled back out to start on the clit once more. Twilight moaned quietly as Rainbow teased the sensitive little button. By Celestia, I love the noises she makes. Rainbow tweaked it with her mouth and then rubbed her nose against it. Finally, she pursed her lips tightly and suckled it. Beneath her, Twilight shook, and Rainbow grinned.

Twilight came again, as wet and wild as the first time. Rainbow covered Twilight's pussy with her mouth, riding it up and down as her pelvis pulsed. Juicy squirts filled her mouth, and she drank them down like honey. Twilight's spasms continued for what seemed like ages, but Rainbow stayed on her for the duration.

At last, the shudders subsided. Rainbow licked up the last few drops, savoring the taste. Twilight's chest was heaving under her, and her butt was still clenching and unclenching as the muscle twitches faded. Rainbow leaned down and planted a long, tender kiss on Twilight's damp, pink folds.

She crawled back up around to Twilight, finding the unicorn's face flushed blank with ecstasy. She gave her a light peck on the cheek, leaving a wet mark. Twilight rolled her head over and smiled, her eyes half-lidded with sleepy satisfaction. "Kiss me again."

Rainbow closed her eyes and complied. Their lips met in the best kiss she had ever had. It wasn't as passionate or invasive as their earlier one, but it was warmer and deeper and filled with some elusive quality Rainbow thought she might label intimacy. They melted into each other, and Rainbow wrapped her forelegs around Twilight to pull her closer.

When did this go from simple rutting to making love? Rainbow's mouth took a brief detour to suck on Twilight's bottom lip, before rejoining the kiss. I think Twilight said it, earlier. We know each other inside and out, better than we ever could have without those potions. Wherever you are, Zecora... thanks.

Finally, they pulled their mouths apart. Nuzzling her head up against Twilight's shoulder, Rainbow sighed in total satisfaction. They cuddled for a few minutes, gently rubbing their hooves on each other's fur, relaxing in the aftermath of nearly three hours of lovemaking.

Rainbow opened her eyes and kissed Twilight's neck again. "So, what now?"

"Now?" Twilight hugged her. "I don't know. I've never felt this happy and, and... full, before."

"Full? Twilight, I'm a mare again, remember?"

Twilight kissed her again. "It's a different kind of full."

"I know what you mean," said Rainbow with a smile, tracing Twilight's cheek with a hoof. "Me too."

They lay together for a little while, lost in each other's eyes. Rainbow felt like she could spend the rest of the week in bed with Twilight, just sitting like this, holding each other. She smiled. "We could go to sleep."

Twilight laughed. "I may have to buy a new bed, first." She ran a hoof through Rainbow's multicolored hair. "Your mane is beautiful, Rainbow, have I ever told you that?"

"Yes," said Rainbow, looking into Twilight's eyes and grinning. "But you can tell me again."

Twilight rolled her eyes and closed them. Her mouth curled. "Aha, that's what we should do."

"Hm?"

"Take a bath."

Rainbow murmured in agreement. "Is your tub big enough for two?"

"Sure is." Twilight opened her eyes happily. "Let's go put some bubbles in the water. I want to wash your mane. I made a bit of a mess in it earlier, and I want to make it up to you."

"Okay," said Rainbow, rubbing Twilight's belly. "When you're done, I'd be happy to return the favor."

"Thank you," said Twilight, giving her one more kiss on the lips. "For everything."

Rainbow dived through the cloud, bursting from the other side with a mighty flap of her wings. She shook herself, raining little droplets of water down toward the ground far below. Looping up again, she spotted her floating house, making a beeline for the entrance.

She landed by the mailbox, stretching her legs in post-flight cooldown. Ponyville would be having another gorgeous morning, thanks to her efforts. Rainbow smiled and checked her mail. The postmare had been by, and she found a cluster of letters inside.

Flipping through them as she walked up to her front door, Rainbow folded her wings to her sides. "Bill... bill... ad... bill..." She paused, finding a lavender purple envelope in the stack. "From Twilight..." Opening the letter with a spark of excitement, she scanned the words.

Dear Rainbow Dash,

It's been three weeks since you helped me run those potion experiments, and I'm happy to report that I've finally gotten some results. Now, normally I'd go over the data with Spike, but I'm afraid he's going to be busy all day running a list of errands for me. A very long list. Since you were so instrumental in the tests, I thought you might like to come over and have a look. I had Zecora mix up a few more bottles, to ensure our experiment can be repeated with full scientific rigor. I've cleared my whole afternoon. If you're interested, please come over at your earliest convenience.

Love, Twilight Sparkle

P.S.: I've been working on a new cotton waterproofing spell I think you'll like.

P.P.S.: It's so hot out! Bring some water with you. We may need to re-hydrate.

Rainbow finished the letter with a smile. She dropped the letters on her doorstep. "Of course I'll come," she said, laughing. "After all, I am a great lover of the sciences."

Grabbing a fluffy bit of cloud to use for drinking water later, Rainbow took off. Her body floated down toward Ponyville, but her heart soared up into the sky, flying high with delight and anticipation. As the library grew larger below her, Rainbow's eyes narrowed, and she grinned. She couldn't wait to explore more of the possibilities of potions.


End file.
